The present invention relates to a rotor structure for rotary wing aircraft, such as helicopters having a rotor head on which the rotor blades or wings are supported for rotation without any lagging hinges or without any lagging hinges and without any flapping hinges, however in a non-rigid manner, whereby, in the case of a four wing rotor structure, to tension bars which cross each other, interconnect the rotor blades in pairs. The tension bars are resistant or substantially resistant against tension stress and bending moments. The tension bars are supported on the rotor head by a bearing means which are angularly movable in the lead-lag direction and which are radially spaced on both sides from the rotational axis of the rotor shaft.
In connection with conventional rotor structures for rotary wing aircraft it is not avoided that the common mass center of gravity of two rotor wings arranged diametrically opposite each other, is displaced radially outwardly from its central position coinciding with the rotational axis of the rotor shaft. Such displacement or excursion takes place when the two wings do not lead-lag in the same direction simultaneously and/or when they do not lag by the same angle. Such an excursion of the center of gravity is largest when the lag angle is of equal size for both wings while the wings of a pair arranged opposite each other lag in opposite lagging directions. This condition is referred to as the so-called symmetric lag-bending form. As a result of such a lag-bending form, a temporary mass unbalance is produced which subjects the rotor and its bearing means to substantial loads. Besides, such lag-bending form causes rather very disturbing vibrations.